Alternating-current motor.



M. MILGH.

ALTERNATING CURRENT MOTOR.

APPLICATION TILED DEG. 23,1903.

Patented Apr. 20,1909.

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UNITED STATES r rnur orric.

MAURICE MILCH, OF SCHENEOTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALTERNATING-GURRENT Moron.

Specification of Letters Patent.

Patented April 20, race.

Application med December 28, 1903. Serial Nb. 188,363.

To all whom it 'ma/y concern:

Be it known that I, MAURICE MILoH, a subject of the King of Hungary, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Alternating-Current Motors, of which the followin is a specification.

l y invention relates to the control of alternating-current motors of the repulsion tlge, andits object is to provide simple, e cient and reliable means for so controlling such motors as to produce a strong braking effect upon a car or other body driven by motors of this type.

The direction of rotation of a repulsion motor depends upon the relative positions of the line of magnetization of the primary member and the commutator brushes of the secondary member. The direction of rotation can consequently be reversed by shifting the position of either the line of magnetization or the brushes. A simple method of reversing the motor consists in providing two sets of terminals, one set on each side of the brush position, and connecting one set or the other to the source of current according to the direction of rotation desired. A motor thus rovided with two sets of terminals mi ht e braked by shifting the connection 0 the source from one set of. terminals to the other. This method of braking, however, would be impractical, since it would not only draw an extremely large current from the line, but the shock upon the motor and the body driven thereby would be excessive. I have discovered, however, that by taking advantage of the residual magnetism of the motor a strong braking effect may be obtained which is not .too violent and which may readily be controlled in amount.

My invention will be best understood by reference to the accompanying drawings, in which-- Figures 1 and 2 are diagrams explanatory of my invention, and Fi 3 shows an arrangement of switches an circuits embodyin :my invention. aafnrhig first to Fig. 1, 8- represents the stator of a repulsion motor having two sets of terminals a o and b b. It represents the rotor of the motor having the ordinary short-circuiting brushes 0 disposed midway between the two sets of stator terminals. In the figure, terminals 6 b are shown connected to the mains 1 2 through the switch D. The motor will consequently revolve in a counter-clockwise direction according to the well known repulsion principle. Now if switch D is o ened, disconnecting terminals b b from t e line, and if switch E is closed, short-circuiting the other set of terminals a a, the residual magnetism of the motor will cause a current to flow in the motor winding which will react upon the short-circuited stator Winding and upon the magnetism of the motor in such a manner that the magnetism and the currents in both short-circuited members will be increased. The eiiect is cumulative and large currents Will be almost instantaneously produced, resulting in a strong braking action. In practice this cumulative eiiect is too sudden, producing too severe a shock upon the motor and the car if both primary and secondary windings are directly shortcircuited. In order to reduce the shock a variable impedance ma be inserted in the circuit of either mem er. Thus, I have shown in Fi 1 the primary or stator terminals a a s ort-circuited through the variable resistance I. By short-circuitin the primary member through the whole of this resistance at first and then gradually reducing the amount of resistance included in the short-circuit as the motors slow down the braking efiect may be readily controlled.

As has been said, the variable impedance may be inserted in the short-circuit of either the primary or secondary member, and the current flow in both short-circuits will be controlled thereby in either case. Furthermore, instead of the variable resistance 1 of Fig. 1, other forms of variable impedance may be used. Thus, in Fig. 2 I have sh wn a source of back-electromotive force as varicuit of the secondary member. The transfomnerThas tapsfrom its secondary winding led out to switch contacts adapted to be engaged by the switch member t which is connected in circuit with the brushes c of the this means, andfurthermore instead of diss1- y and the main controlling-switch G.

pating the energy developed in heat, as in the arrangement of Fig. 1, the energy is returned to the line by the arrangementshown in Fig. 2.

Referring now to Fi' 3, anarrangement of switches is shown a apted to the control of one or more motors in such a manner as to operate them in either direction and to produce a braking action when desired \while they are rotating in either direction. The switches consist of the reversing-switch F The reversing-switch consists oi the stationary contacts j etc, and two sets of movable contacts 5 etc. and m m etc, the sets of movable contacts corresponding to the forward and reverse rotatlon of the motors. The controlling-switchG comprises the stationary contact fingers k W, etc., and the two sets of movable contacts n n and 0 0 etc.

\ stationary so that t n n 'are the running contacts and o 0 etc, are the braking contacts. Thus, if reversin =switcl1 F is moved so that the contacts 1 1 etc., are in engagement with the contacts, and-switch G is moved gagement with the stationary contacts, the motor-circuits are as follows: from line wire 1 to contact-finger j, to movable. contact Z to stationary contact-fingery', to u per terminals a a of the motors throug stator windings S and S in parallel, to lower terminals a a, to-stationary contact-finger 7c, movable contact a, stationar contact id, to

. stationary contact 1', mova le contact Z stationary contact 7' to line wire '2. If

switch G'should be moved to its other position the stator circuits from the terminals a a would be opened at contact-fingers 7c and 1765. Anew circuit is established,'however, as follows: fromupper stator terminals b and b contact-finger j, movable contact Z, contact finger'j", contact-finger 7a through resistance I, contact-finger 7c, movable contact o, movable contact 0 contact-finger kt, contact-fingerjfi movable contact Z contactfinger 3' to lower terminals?) and b. The

' terminals 6 b and b t? of the motors are contil direction of rotation ofthe motors sequently short-circuited throu h the resistance l'. he switch G is move through its other braking positions, resistance I is gradually cutout, until inthe last position of switchG the stator terminals are directl short-circuited. It will be seen thatif switch F is moved to its opposite. position and the movable contacts m m etc. are m engagkpment with the stationary contact-finggfifi,l the e e running contacts n n are in enerases evident from the drawing, and it will be un-' pecessary to describe the circuits in detail ere. e

In order to avoid complicating the drawings, switch G has been shown without er rangements for shifting the motors from serice to parallel or other similar. speed-controllin arrangements. It will be understood, owever, that additional runnin contacts may be provided if desired, an connected in any of the ways well known in the art without departing from my invention. Furthermore, as has been already explained, the variable resistance may be introduced in the short-circuit of the secondary member or other forms of variable impedances may be used. ()ther chan es in the arrangement of the controlling devices for the motor may be introduced Without departing from the spirit of my invention. For instance, since the braln'ng efi'ect depends solely upon the relative direction of displacement ofthe commutator brushes and the primary terminals, any well known form of brush-shifting device may be used to obtain the relative reversal of the displacement instead of employing the means for shifting the terminal connections with the primary member.

I do not desire to limit myself to the particular construction and arrangement of parts here shown, since changes therein which-d0 not depart from the spirit of my invention and which are in the scope of the a ended claims, will be obvious to those s 1 led in the art.

What I claim as new and desire to secure verse rotationrespectively, a source of alternating current, and a switch adapted to connect one set ofterminals to said source and to disconnect said set from said source and to connect the second set in short-circuit.

. 3. In combination, a repulsion motor having two sets of terminals for forward and re verse rotation respectively, a source of alternating current, means for connecting and disconnecting one setgof terminals to and from said source, means for short-circuiting the other set, and means" for controlling the amolmt of cur'rentfifow in the short-circuit.

4. In combination, a repulsion motor hav ing two sets of terminals tor forward and reverse rotation respectively, a source of alternatin current, a switch adapted to connect and isconnect one set of terminals to and from said source and to connect the other set in short-circuit, and means for controlling the amount of current flow in the short-circuit.

5. In combination, a repulsion motor having two sets of terminals for forward and reverse rotation respectively, a source of alternating current, means for connecting and disconnecting one set of terminals to and from said source, and means for short-circuiting the other set through a variable impedance.

6. In combination, a repulsion motor having two sets of terminals on its primary member for forward and reverse rotation respectively, a source of alternating current, means for connectin one set of terminals to said source and s ort-circuiting 'the secondary member of the motor, and means for disconnecting said set of terminals from thesource, short-circuiting the other set, and inserting a variable impedance in the circuit of the secondar member. A

7. Iii combination, a repulsion motor hav ing two sets of terminals for forward and reverse rotation respectively, a source of alternating current, means for connecting one set of terminals to said source, means for disconnecting said set from said source and for connecting the other set in short-circuit, and means for returning the energy thereby generated. to said source.

8. In combination, an alternating-current motor having a primary member and a secondary member provided with a commutator and short-circuiting brushes, a source of alternating current, means for connecting said source to sald primary member to produce a magnetization thereof on a line displaced from the line of said brushes, and means for disconnecting said primary member from said source and short-circuiting said primary member on a line displaced in the other d1- rectionfrom the line of said brushes.

9. In combination, an alternating-current motor havin a primary member and a secondary mem er provided with a commutator and short-circuiting brushes, a source of alternating current, means for connecting said source to said primary member to produce a magnetization thereof on a line displaced from the line of said brushes, means for di" connecting said primary member from said source and short-circuiting said primar member on a line displaced in the other di rection from the line of said brushes, and means for controlling the amount of current flow in the short-circuit.

10. In combination, a repulsion motor, a source of current therefor, and means for disconnecting said motor from said source and short-circuiting the primary member of said motor, with a relative displacement of the line of the commutator brushes and the line of the short-circuit of the primarymember opposite to the relative displacement or" the line of the commutator brushes and the'line of magnetization of the primary member when connected to'the source;

11. In combination, a repulsion motor, a source of current therefor, means for disconnecting said motor from said source and short-circuiting the primary member of said motor, with a relat ve displacement of the line of the commutator brushes and the line of the short-circuit of the primary member opposite to the relative displacement of the line of the commutator brushes and the line of magnetization of the primary member when connected to the source, and means for controlling the amount of current flow in the short-circuit.

12. Themethod of braking an alternating current motor having a rotor provided with a commutator and short-circuitingbrushes, which consists in disconnecting the motor from the source, and connecting the motor for rotation in the opposite direction with its terminals short-circuited.

'13. The method of braking an alternatingcurrent motor havin a rotor provided with a commutator and s ort-circuiting brushes, which consists in disconnecting the motor from the source, and connecting the motor for rotation in the opposite direction with its terminals short-circuited and controlling the current in the short-circuit.

14. The method of braking a repulsion motor which consists in disconnecting said motor from its source of supply and shortcircuiting the primary member of said motor, with a relative dis lacement of the line of the commutator brus es and the line of the short-circuit of the rimary member opposite to the relative displacement of the line of the commutator brushes and the line of magnetization of the primary member when connected to the source.

15. The method of braking a repulsion motor which consists in disconnecting said motor from its source of supply, short-circuiting the primar member of said motor with a relative dis acement of the line of the commutator brus hes and the line of the short-circuited primary opposite to the rela tive displacement of the line of the commutator brushes and the line of magnetization of the primary member when connected to the source, and controlling the amount of our rent flow in the short-circuit.

16. The method of controlling a repulsion motor having two sets of terminals for forward and reverse rotation respectively, which consists in disconnecting from the source of supply the set of terminals connested thereto and; short-circuiting the other and controlling the amount of cufrent flow set. V through the short-circuit. 10

17 The method of controlling a repulsion In witness whereof, I have hereunto set my motor'heving two sets of termma'ls tor forhand this 21st day of Deoember, 1903.

5 ward and reverse rotation res ectively, MAURICE MILCH.

which consists in disconnecting om the Witnesses: source of supply the set of terminals con- BENJAMIN B. HULL, nested thereto, short-eircuiting the other set, HELEN @RFORD. 

